Magnetically compensated sensitive relay



May 4, 1954 E. H. BEACH MAGNETICALLY COMPENSATED SENSITIVE RELAY 2 Sheets-Sheet 1 INVENTOR EUGENE H. BEACH g ooooooooooo gg Filed June 25, 1952 ATTORNEYS May 4, 1954 E. H. BEACH 2,677,735

MAGNETICALLY COMPENSATED SENSITIVE RELAY Filed June 23, 1952 2 Sheets-S heet 2 INVENTOR EUGENE H. BEACH BY Rm. 141% ATTORNEYS Patented May 4, 1954 UNITED STATES i ATENT OFFICE MAGNETICALLY COMPENSA'IED SENSITIVE RELAY (Granted under Title 35, U. S. Code (1952),

sec. 266) 10 Claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to a relay of the typ commonly known as a Sensitrol relay which is highly sensitive and yet can withstand high accelerations without requiring special cushions or mounts.

Heretofore, relays which were designed to be actuated upon the passage of current through the operating coil were either not capable of withstanding high shocks or were not sufficiently sensitive to small amounts of current. The necessity for a highly sensitive relay of rugged construction is apparent when considering that such relays are frequently used in the firing circuit of a mine and must be capable of withstanding the high shocks encountered when the mine is laid and yet be capable of responding to small variations in the magnetic field surrounding the mine caused by the movement of a ship. Relays which were capable of responding to small variations in the magnetic field usually included jewelled bearings and accurately formed pivots. However, such relays could not withstand the high shocks hereinbefore referred to. On the other hand, relays which employed heavier suspensions of more rugged construction for the movable contact arm could not respond to small current variations due to the opposing torque developed by the suspensions.

The present invention overcomes the difiiculties referred to above by providing a relay in which the movable contact arm is suspended by strips of relatively strong metal so that the device is capable of withstanding high shocks. The disadvantages inherent in such a construction are obviated by providing a compensating magnetic Y field adjacent the end of the movable contact arm which acts in opposition to the torque produced by the suspensions. nent field magnet adjacent each end of the arc of movement of the movable contact arm and extending between these magnets are field pole pieces so that the flux or these magnets is substantially uniformly distributed throughout the air gap. Mounted on the end of the contact arm is a permanent magnet the flux of which is additive to the flux of the field magnets. A plurality of compensating screws are located within one of the field pole pieces and these are adjusted so that a compensating field is produced which uniiormly increases in strength from the center to- There is provided a perma-' 2 wards each field magnet thereby effectively counteractin the opposing torque of the suspensions which varies from zero when the movable contact arm is in a center position to a maximum when the arm is at a maximum deflection. In this manner a relay is provided which requires a small amount of current for actuation and will respond uniformly regardless of the angle of deflection or" the movable contact arm.

A primary object of this invention is the provision of a relay which is of rugged construction and yet highly sensitive.

Another object or" this invention is to provide a relay in which the operating coil is suspended by strips of relatively strong metal and. in which a compensating field nulls out the torque of the suspension.

Still another object of this invention is to provide a relay in which the sensitivity may be readily adjusted to suit various operational requirements.

Other objects and many of th attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. 1 is a top plan view of the relay;

Fig. 2 is an end elevation of the relay;

Fig. 3 is a side elevation of the relay; and

Fig. 4 is a sectional view along the line 4-4 Of Fig. 1.

Referring now to the drawings wherein like numerals indicate like parts throughout the several views there is shown in Fig. l the relay I having a base plate 2. Mounted on this base plate is a pair of supportin blocks 3 (Fig. 3) upon which is mounted a permanent magnet 4 having poles 5 and t. On the upper surface of the magnet 4 is mounted a pair of supporting members i which serve to support cross piece 8. Suitably secured to this cross piece and insulated therefrom is a spring suspension support 9 on the outer end of which is mounted grip l I. Mounted on base 2 and insulated therefrom is a spring suspension support It on the outer end of which is mounted grip l3.

Securely mounted Within the .air gap between poles 5 t of magnet 4 as by plates M and E5 (Fig. 4) is a soft iron core It. The operating coil ll of the relay is provided with grips l8 and IQ and is rotatably supported between poles 5 and 5 and core 56 by means of gold foil strips 2! and 22 which extend between grips II and it and grips l3 and I9 respectively.

Guards 23 and 3 24 suitably secured to permanent magnet 4 permit rotation of coil I1 and prevent undue strain on the suspension due to sudden shock. Secured to grip l9 and extending therethrough is a con tact arm having a counterweight 26 mounted on one end thereof. Current is supplied to the operating coil directly through the suspension supports either from a detection coil (not shown) or other desired source and it is obvious that the coil will rotate within the air gap between poles 5 and E and core It in response to current flow thereby causing movement of contact arm 25.

Extending upwardly from base 2 are bolts 21 which serve to support plate 28 on which are fixed the resetting solenoids 29 and 30 which are similarly wound and a centering solenoid 31 which is oppositely wound. A permanent magnet 32 is mounted on the contact arm 25'(Fig. 4) and, when the arm moves in response to current flow within the operating coil, this magnet will be attracted to the cores of the resetting solenoids 29 and 30. The cores of the resetting solenoids extend into engagement with the magnet on the contact arm, and the circuit in which the relay is used is completed by this contact. When current is supplied to the solenoids, the magnet on the contact arm is repelled by the resetting solenoids and is attracted by the oppositely wound center ing solenoid. The core of this solenoid does not engage the contact arm but will serve to hold the arm in the center or neutral position as long as the solenoid is energized.

It is apparent that, as the contact arm moves from the center position, an opposing torque will be developed by the suspensions 2! and 22. In order that a uniform amount of current will move the contact arm from the center position into engagement with either of the resetting solenoid cores, it is necessary to compensate for this torque. This is accomplished by a means to be now described in detail. Mounted on base 2 and extending upwardly therefrom are bolts 33 (Figs. 3 and 4) which support pole pieces 34 and 35 (Fig. 2) having permanent magnets 36 and 31 secured to the ends thereof. These magnets have similar poles thereof in alignment so that a field of substantially uniform intensity is provided within the air gap between the pole pieces. Mounted within the pole piece 35 is a plurality of soft iron screws 38 which are adjusted substantially .as shown in Fig. 2 to vary the size of the air gap between the pole pieces. It can be seen that a held of increased intensity is provided adjacent the ends of the arc of movement of the contact arm. The magnet 32 is vertically disposed so that the ileld thereof is additive to the field produced by the compensating magnets 38 and 37. It can be seen, therefore, that the field of the magnets 35 and 3? produces a force on the contact arm which balances or compensates for the torque of the suspension strips 2i and 22.

There is provided a plastic plate 39 within the air gap between the pole pieces which serves as a guard to prevent substantial movement of contact arm 25 due to sudden shock. Iron shields 4t and M mounted on base 2 prevent the fields produced by magnets and 3'! from influencing the operation of coil ll within the air gap of magnet 4.

The theory of operation of the presently disclosed relay is as follows. The suspension means for the operating coil H has a certain spring constant (Ks) and the torque exercised by the suspension means on the movement of the contact arm for an angle of rotation 6 may be expressed: Ts=Ks9. The torque produced in the operating coil for a given current (i) is: Te=cmi. The constant c is determined by the number or turns .and the length of the operating coil and m is the flux in the air gap of the main magnet. The compensating screws 38 are adjusted so that the effect that the compensating field has on the magnet 32 produces a torque for any angle of deflection equal to Tm Ts Tc. Transposing gives To Ts Tm Cmi =Ks0 Tm.

Let the compensating screws be so adjusted that the forces acting on the magnet 32 produce a torque proportional to the angle of deflection. Let Km be the proportionality constant and the above equation becomes: cmi=Ks0-Is.'m6. Di- Viding by 04ml gives:

From this equation it is obvious that the current 2' required for operation can be made very small and the relay can be made very sensitive by adjusting the compensating screws so that Km is nearly equal to Ks.

It is apparent, therefore, that there has been provided a relay which is of rugged construction and capable of withstanding high shocks and which, nevertheless, will respond to a small current flow.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed as new and desired to be secured by Letters Patent is:

i. In a device of the class described, means roviding a magnetic field, a coil having an secured thereto, means for suspending coil for rotation within said field, and magnetic means for continuously compensating for the torque of said suspension means throughout the travel. oil the arm, said torque being caused by movement of said arm from a neutral position.

2. In a measuring instrument of the class described, means providing a first magnetic field, a coil having an arm secured thereto, suspension means for pivotally supporting said coil within said field, and compensating means including means providing a second magnetic field, and a permanent magnet mounted on the end of said arm for continuously equalizing the torque of said suspension means through the entire path of travel thereof, said torque being caused by movement of said arm from a neutral position.

3. In a device of the class disclosed, a permanent magnet, a coil having a movable arm secured thereto, suspension means including gold foil strips for rotatably supporting said coil within the field of said magnet, and means for compensating for the torque of said suspension means, said torque being caused by movement of said arm from a neutral position, said compensating means including a permanent bar magnet secured to the movable arm and magnetic means for producing a field of continuously varying strength in proportion to said torque and along the path of movement of said bar magnet.

4. In a device of the class described, means including a movable coil and arm for detecting a small amount of current, suspension means for said coil including gold foil strips and compensating means including means for producing a field of continuously increasing strength for equalizing the torque of said suspension means caused by deflection of said arm from a neutral position.

5. A sensitive relay comprising, in combination, means providing a magnetic field, a moving coil having a contact arm secured thereto, suspension means for pivotally supporting said coil within said field, said contact arm having a permanent magnet secured to the end thereof, a contact of magnetic material secured adjacent each end of the arc of movement of said arm, means for resetting and locking said contact arm in a neutral center position, and means for providing continuous compensation for the torque of said suspension means caused by deflection of said contact arm from the neutral position.

6. The combination of claim 5 wherein said compensating means includes means for producing a field additive to the field of said permanent magnet.

'7. In a sensitive relay of the class disclosed, a permanent magnet, a coil having a contact arm affixed thereto, suspension means for pivotally mounting said coil including foil strips, said contact arm having a magnet mounted on the end thereof, means for locking said contact arm in a center and deflected positions, means for resetting said arm from a deflected to a center position, and means for compensating for the torque of said suspension means, said torque being produced by movement of said contact arm from a center position to a deflected position, said compensating means including magnets mounted in parallel and having the field thereof additive to the field of said magnet on the contact arm and said means further including a plurality of screws whereby the intensity of said field may be varied.

8. A relay comprising, in combination, means including a movable contact arm for detecting a small amount of current whereby said contact arm is pivoted in response thereto, means for compensating for the torque of said first-named means caused by deflection of said movable contact arm, said last-named means including magnets mounted adjacent the ends of the path of movement of said contact arm and having soft iron pole pieces mounted therebetween whereby a uniform field is produced within the air gap between said pole pieces, said contact arm having a permanent magnet mounted thereon whereby the field thereof is additive to said uniform field, said last-named means further including a plurality of adjusting screws mounted within one of said pole pieces whereby the intensity of said uniform field may be varied.

9. A sensitive relay comprising, in combination, a permanent magnet, a coil having a contact arm secured thereto, suspension means including foil strips for pivotally supporting said coil Within the field of said permanent magnet whereby said contact arm will move in response to a flow of current within said coil, said contact arm having a permanent magnet mounted on the end thereof, contact members fixedly mounted at the ends of the path of movement of said contact arm, means for resetting and locking said contact arm in a neutral center position, permanent magnets mounted adjacent the ends of the path of movement of said contact arm and having pole pieces extending therebetween, the permanent magnet on said contact arm adapted to move in the air gap between said pole pieces,

" and a plurality of screws mounted within one of said pole pieces to vary the size of the air gap between said pole pieces and thereby vary the intensity of the field whereby the torque of said suspension means caused by deflection of said contact arm may be compensated for by increasing the intensity of the field of said pole pieces adjacent the end portions of the path of movement of said contact arm.

10. In a sensitive relay of the character described, a permanent magnet, a coil having a contact arm affixed thereto, means for rotatably mounting the coil in the field of said magnet, said means tending to maintain the arm in a neutral position, magnetic means carried by said contact arm, and means comprising a pair of magnets mounted in parallel and having the field thereof additive to the field of said magnetic means on the arm for providing a continuously increasing magnetic field of a character to compensate for the torque of said coil mounting means.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,427,093 Cox Aug. 29, 1922 2,341,412 Paulson Feb. 8, 1944 2,494,622 Lamb Jan. 1'7, 1950 2,603,730 Pethes July 15, 1952 OTHER REFERENCES Magnetism and Electricity, Brooks and Poyser (London), 1927. 

